ch10 physics

A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in

0.5 s.

A stone is thrown horizontally from the top of a cliff. One second after it has left your hand, its vertical distance below the top of the cliff is

5 m.

When no air resistance acts on a fast-moving baseball, its acceleration is A downward, g. B a combination of constant horizontal motion and accelerated downward motion. C opposite to the force of gravity. D centripetal.

A downward, g.

Projectile:

Any object that moves through the air or space under the influence of gravity, continuing in motion by its own inertia

A cannonball is fired horizontally at 10 m/s from a cliff. Its speed 1 second after being fired is about A 10 m/s B 14 m/s C 16 m/s D 20 m/s

B 14 m/s One second after being fired both its horizontal and vertical components of velocity are 10 m/s. By the Pythagorean theorem, the resultant is 14.1 m/s, a bit more than 14 m/s.

Neglecting air drag, a ball tossed at an angle of 30◦ with the horizontal will go as far downrange as one that is tossed at the same speed at an angle of A 15◦ B 45◦ C 60◦ D 75◦ E none of the above

C 60◦ because 30+60= 90

Parabola:

Curved path of a projectile that undergoes acceleration only in the vertical direction, while moving horizontally at a constant speed

Rockets that launch satellites into orbit need less thrust when fired from

Hawaii.

Different horizontal distances same range? when the angles add up to? maximum range occurs for ideal launch at?

Same range is obtained from two different launching angles when the angles add up to 90◦ Maximum range occurs for ideal launch at 45◦

A ball is thrown upward at an angle. What happens to the horizontal component of its velocity on the way down?

The horizontal component of velocity is not changing horizontal motion with constant velocity.

Projectile motion is a combination of

a horizontal component, and a vertical component

A bullet fired horizontally from a rifle begins to fall

as soon as it leaves the barrel.

Projectile Motion With gravity, the same object tossed at an angle follows a

curved path.

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its vertical component of velocity

decreases.

According to Kepler's laws, the paths of planets about the sun are

ellipses.

It takes Pluto a longer time to orbit the sun than the Earth does because Pluto

goes much slower.and has much further to go.

The Early Bird communication satellite hovers over the same point on Earth's equator indefinitely. This is because

its orbital period is 24 hours.

A "weightless" astronaut in an orbiting shuttle is

like the shuttle, pulled by Earth's gravitation.

Compared to the period of satellites in orbit close to the Earth, the period of satellites in orbit far from the Earth is

longer.

A lunar month is about 28 days. If the moon were farther from the Earth than it is now, the lunar month would be

more than 28 days.

An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is

nearest the Earth.

The tangential velocity of an Earth satellite is its velocity

parallel to the surface of the Earth.

Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity

remains constant.

Acceleration due to gravity on the moon is less than on Earth, and the moon is smaller than Earth. So compared to an Earth satellite, a satellite in close orbit about the moon would travel the same. faster. slower. Not enough information is given to say.

slower.

Which of the following is not a vector quantity?

speed

Projectile Motion without gravity a tossed object follows?

straight-line path

The fastest moving planet in a solar system is

the planet nearest the sun.

A crystal sphere rolls off a horizontal table top, drops onto the floor and breaks. If it were rolling slower, would it hit the floor with a lower speed and possible avoid breaking? Why or why not?

...

Without air resistance, the time for a vertically tossed ball to return from its highest point to where it was thrown is A 10 m/s for every second in the air. B the same as the time going upward. C less than the time going upward. D more than the time going upward.

B the same as the time going upward.

Horizontal component of velocity doesn't change (when air drag is negligible). so the ball travels?

Ball travels the same horizontal distance in equal times (no component of gravitational force acting horizontally).

The velocity of a typical projectile can be represented by horizontal and vertical components. Assuming negligible air resistance, the horizontal component along the path of the projectile A increases. B decreases. C remains the same. D Not enough information. because?

C remains the same. Since there is no force horizontally, no horizontal acceleration occurs.

A ball is thrown upward at an angle. What happens to the vertical component of its velocity on the way up?

During the time the ball is rising, its vertical component of velocity is changing from positive (upward). vertical motion with constant acceleration

An Earth satellite is simply a projectile

Freely falling around the Earth.

Vertical positions become farther apart with time. so what happens to the ball?

Gravity acts downward, so ball accelerates downward.

Velocity of projectile following a parabolic trajectory..what remains unchanged? what changes? velocity at any point is computed with?

Horizontal component along trajectory remains unchanged. Only vertical component changes. Velocity at any point is computed with the Pythagorean theorem (diagonal of rectangle).

Curvature of path is the combination of? Parabola: Curved path of a projectile that undergoes acceleration only in the vertical direction, while moving horizontally at a constant speed

horizontal and vertical components of motion.

A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of velocity because

it is not acted on by any horizontal forces.

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity

remains unchanged.

A projectile is fired vertically from the surface of the Earth at 8 km/s. The projectile will

rise and fall back to the Earth's surface.

Without air resistance, the time for a projectile to reach maximum height is the?

same as the time for it to return to its initial level